Disclosed herein are techniques for rotor identification associated with atrial fibrillation (AF) or ventricular fibrillation (VF), such as to, for example, improve catheter ablation or pacing procedures in cardiac pacemakers.
Over two million people in the United States are currently afflicted with AF, which may be the most common sustained cardiac arrhythmia in humans, and many more cases are predicted in the near future. AF is also considered to be a cause of stroke.
Antiarrhythmic drugs are only partially effective and can cause serious side effects, including life-threatening arrhythmias. Despite great strides in understanding of AF, therapy using pharmacological, percutaneous and surgical interventional approaches remains suboptimal.
A limitation of therapy is the lack of mechanistic understanding for AF. However, it has recently been demonstrated that paroxysmal AF in patients is initiated by focal triggers localized usually to one of the pulmonary veins (PV) and can be remedied by a catheter-based ablation procedure. However, in persistent AF, the location of triggers is unclear; and therefore, therapy can be challenging. While advances have been made in ablating PV AF triggers in persistent and permanent forms of the arrhythmia, triggers may arise outside of PV, and extra-PV substrate plays an important role in arrhythmogenesis and maintenance of AF.
Catheter ablation is associated with limited success rates in patients with persistent AF. This may be the case because persistent AF is known to be at least partially caused by rotors, such as rotors located outside of the PV, and known mapping systems can predict locations of rotors outside of the PV in patients with persistent AF to some extent.
Known processing methods that are used to identify AF vulnerable regions of the heart include analysis of the dominant frequency (DF), complex fractionated electrograms (CFAE), phase analysis and local activation time (LAT) maps. These techniques can be based on temporal analysis of electrograms from different spatial locations of atria. However, the high frequency of recurrence of arrhythmias in patients with persistent AF after PV isolation and ablation shows that the current processing methods for AF analysis may not be adequate to predict critical areas of AF maintenance, such as locations of rotors. Also, known electro-anatomic mapping systems (such as ENSITE, NAVX, and CARTO) that employ known signal processing techniques (DF, CFAE, and LAT) may not be able to adequately predict a rotor's location outside of PV in patients with persistent AF. For example, the aforementioned mapping techniques may fail since clinical signals may not represent local activation. Also, virtual electrograms from non-contact methods may distort information in AF.
Data supports localized sources by reentrant mechanisms for AF showing that AF may be sustained by stable drivers such as electrical rotors. The pivot points of such rotor waves are believed to be good ablation targets to terminate AF in patients. About 77.8% success rate has been demonstrated by ablation of such sites in paroxysmal, persistent, and long-standing AF patients.
However, known mapping methods used for guiding catheter ablation, such as LAT maps and CFAE—mean index maps, have numerous limitations in their ability to accurately identify rotor pivot zones. This can be due to noise and misleading phase and activation times that distort these maps.
Thus, there are problems to be solved. For instance, there is room for improvement with spatiotemporal mapping technology that can identify the rotor pivot points in a patient-specific manner.